Messing with USB

I am trying to read the vendor ID (and later, product ID) from a USB device. Primarily to see what sort of facilities are available other than reading/writing the DeviceFS file.

Unfortunately, all I get is “Bad request”. Am I doing something obviously wrong? Do I have to open endpoints before I can do this?

REM Attempt to read Vendor ID from USB device

DIM buffer% 32
usb$ = "USB1" : REM Use *USBDevices to work out which we want

bmRequestType% = %10000000 : REM Device to Host, Standard, Device is Recipient
bRequest%      = 6         : REM GET_DESCRIPTOR
wValue%        = 1         : REM Descriptor type -> DEVICE
wIndex%        = 0         : REM (unused)
wLength%       = 2         : REM ID is two bytes long

REM ** The following is split for the forum, it should be all on one line **

SYS "DeviceFS_CallDevice", (1<<31), usb$,,
    (bmRequestType% + (bRequest% << 8) + (wValue% << 16)),
    (wIndex% + (wLength% << 16)), buffer%

For reference, I’m using http://wiki.osdev.org/Universal_Serial_Bus#USB_Device_Requests for the USB information, and http://www.iyonix.com/32bit/USBDevFS.shtml for the DeviceFS info.

wValue% needs to be &100 – the descriptor type goes in the high byte of a 2 byte word.

wLength% needs to be 18 (or at least 12) vendor id is bytes 8,9 product id is bytes 10,11